Jan Grepl

Extraction of Blood Vessels Using Multilevel Thresholding with Color Coding

The proposed work deals with the design of algorithm for segmentation of blood vessels in order to extract the geometrical features of analyzed vessels. The algorithm was tested on a sample of 25 clinical data to identify blood vessels direction and suppress surrounding tissues. The proposed methodology is effective for practical purposes, because identifies minor visual differences on the surface of blood vessels. These changes often represent pathological lesions that cannot be identified from the native data. The algorithm is based on the identification of several significant levels to make ideal thresholding, according to object features. For even better diagnostic results image background is subsequently filtered out from the segmented image, background may have a disturbing effect in the diagnosis and the final segmented image contains only analyzed blood vessels.

Real Time Signal Detection and Computer Visualization of the Patient Respiration

The article deals with the realization of the measurement chain for monitoring patient respiratory activity during radiotherapy. The primary requirement is a real time process monitoring of patient respiration during radiotherapy. The main part of the measuring chain is sensing element which converts the patient’s breathing movements into electrical signals. Different possibilities of obtaining these data are described. An essential part of a comprehensive monitoring system is a software environment for the analysis and testing of the acquired data. The output signals which correspond to the ventilation state of the patient are graphically visualized in the user environment, which is created in LabVIEW.

Semi-spherical Radiofrequency Bipolar Device - A New Technique for Liver Resection: Experimental In Vivo Study on the Porcine Model.

The incidence of colorectal carcinoma is still growing in the Czech Republic and also all around the world. With success of oncological treatment is also growing a number of potential patients with liver metastases, who can profit from surgical therapy. The aim of this study was to confirm on porcine models that this method by using new surgical device is effective and safe for patients who have to undergo liver resection. The primary hypothesis of the study was to evaluate whether this new device is able to consistently produce homogeneous and predictable areas of coagulation necrosis without the Pringle maneuver of vascular inflow occlusion. The secondary hypothesis of the study was to compare the standard linear radiofrequency device and a new semi-spherical bipolar device for liver ablation and resection in a hepatic porcine model. Twelve pigs were randomly divided into two groups. Each pig underwent liver resection from both liver lobes in the marginal, thinner part of liver parenchyma. The pigs in first group were operated with standard using device and in the second group we used new developed semi-spherical device. We followed blood count in 0th, 14th and 30th day from operation. 14th day from resection pigs underwent diagnostic laparoscopy to evaluate of their state, and 30th day after operation were all pigs euthanized and subjected to histopathological examination. Histopathological evaluation of thermal changes at the resection margin showed strong thermal alteration in both groups. Statistical analysis of collected dates did not prove any significant (p < 0.05) differences between standard using device and our new surgical tool. We proved safety of new designed semi-spherical surgical. This device can offer the possibility of shortening the ablation time and operating time, which is benefit for patients undergoing the liver resection.

Breathing Movement Analysis for Adjustment of Radiotherapy Planning

Aim of this work is the developing of algorithm, which extract and process the breathing movement data from CyberKnife log files for prospective conventional radiotherapy planning. The described algorithm enable verification and accuracy of the settings radiated tumor rims, which are used in conventional radiotherapy. This results should contribute to improving of the treatment of irradiated tumors with possible subsequent statistical evaluation.

Radiofrequency Instrument for Office Hysteroscopy

The work includes the design and implementation of radio-frequency tools for outpatient hysteroscopy. The research and cooperation with leading professional medical workplace designed a unique system of size 6 Fr. The requirement for a system for the safe bipolar hysteroscopy was respected for the purpose of elimination of soft tissue injury of the uterus. Subsequently BYR implemented and tested a prototype instrument made of ABS plastic resistant to 120 ° C, supplemented by an innovative mechanical system opening. Mechanical tests confirmed the assumption grip and distribution of neoplasms in size 0-10 mm with operating power of 1 - 3.8 N. Radiofrequency excitation was successfully improved with a commercial RF generator RITA 1500x generator operating at 460kHz and 100V. The principle of this newly designed tool is registered with the national, patent Czech Republic.

Pressure Distribution Measurement of Close Fitting Clothes on Human Body

The article introduces research of non-invasive techniques used for measuring of pressure distribution on human skin by the wearing very tight and close fitting clothes. This fact may lead to significant health complications, because long-term constricting of tissue restricts fluid movement around tissue cells which may cause creation of neoplasm. Especially occurrence of tumour in the women breast is diagnosed with ascending tendency. From these reasons was performed research in the area of possible techniques for noninvasive measurement of forces and corresponding pressures on a human skin. Our goal in this part of research was to find the way to measure the pressure distribution between the clothes and the human skin. Through comparison of the results from different devices, the techniques and their potential application was evaluated for future experiments. In addition, we pointed out the weak points and disadvantages of these measurement methods.

Technical development of a new semispherical radiofrequency bipolar device (RONJA): ex vivo and in vivo studies

The aim of this study is to inform about the development of a new semispherical surgical instrument for the bipolar multielectrode radiofrequency liver ablation. Present tools are universal; however they have several disadvantages such as ablation of healthy tissue, numerous needle punctures, and, therefore, longer operating procedure. Our newly designed and tested semispherical surgical tool can solve some of these disadvantages. By conducting an in vivo study on a set of 12 pigs, randomly divided into two groups, we have compared efficiency of the newly developed instrument with the commonly used device. Statistical analysis showed that there were no significant differences between the groups. On average, the tested instrument RONJA had shorter ablation time in both liver lobes and reduced the total operating time. The depth of the thermal alteration was on average 4 mm larger using the newly tested instrument. The new radiofrequency method described in this study could be used in open liver surgery for the treatment of small liver malignancies (up to 2 cm) in a single application with the aim of saving healthy liver parenchyma. Further experimental studies are needed to confirm these results before clinical application of the method in the treatment of human liver malignancies.

A Probabilistic Model of the Interaction between a Sitting Man and a Seat

This article focuses on the biomechanical evaluation of the interaction between load forces to which a sitting man and the seat are mutually exposed. The load forces, which consider actual dispersion in the human population through histograms, are determined using a probabilistic method known as the Simulation-Based Reliability Assessment (SBRA). A simple flat model shows a basic and high-quality stochastic evaluation of all the forces that affect the man and the seat. The results and methodology can be used in many areas of biomechanics, ergonomics or industrial design.